Try this...

https://support.mozilla.org/en-US/questions/1318442

Thank you for the helpful reply. Before I change any values in the registry... I have navigated to HKEY etc to Policies Firefox. Appears as DisableAppUpdate REG_DWORD 0X00000001(1) Do I delete the entry or just change to(0)

Thanks

Just delete the Mozilla or Firefox folder. So that under Polices there is nothing about Mozilla or Firefox under both HKEY_LOCAL_MACHINE\Policies and in HKEY_CURRENT_USER\Policies

Sorry for the update, but I had to boot up my other laptop with Win10 to verify.

What security software do you have?

Note that such an entry is usually added by security software that want to add its root certificate to be able to inspect your internet traffic. Without the imported root certificate you can possibly get an untrusted error message.

• https://support.mozilla.org/en-US/kb/error-codes-secure-websites